The functionality and the properties of triglycerides depend on the ratio and type of fatty acid chains in the molecule. Therefore, triglycerides are used in several ways in nutrition depending on their properties. The fatty acid distribution affects e.g. the nutritional value of a triglyceride. Some fatty acids make the triglycerides high caloric whereas other fatty acids make the triglycerides low caloric. Triglycerides originating from plants etc. are typically high caloric. Triglycerides containing short and long chain fatty acids are low caloric. A special type of low caloric triglycerides are “salatrim” which include at least one long chain saturated fatty acid and at least one short chain fatty acid. Salatrim is an abbreviation of Short And Long chain Acyl TRIglyceride Molecules.
The absorbability and the digestibility of the triglycerides are affected by the fatty acid chains. Triglycerides are also sources of essential fatty acids and their metabolites like linoleic acid and α-linolenic acid, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). They appear in oils originating especially from sunflower, evening primrose, linseed, fish, single cell algae, etc. Thus, some triglycerides are beneficial in nutritional compositions in enteral and parenteral nutrition e.g. for surgery patients, whereas some triglycerides are used in low calorie products for controlling body weight. The fatty acid composition also affects the physical characteristics, such as the melting point of the triglycerides.
Triglycerides with specific fatty acid compositions provide advantages in the food industry, in the nutraceutical industry and the pharmaceutical industry as well as in technical applications such as coating and plasticizing etc. The use of different kinds of triglycerides for various nutritional purposes is well known in the prior art.
EP 0 466 768 relates to a synthetic triglyceride family, which can be used in parenteral nutrition or dietary supplements. The synthetic triglycerides according to the patent have at least one short chain (2–5 carbon atoms) fatty acid.
WO 01/91587 relates to a method for reducing weight gain and maintaining proper body weight, which method consists of administering to an animal an oil composition comprising triglycerides bearing short and medium chain fatty acid residues derived from fatty acids having from 4 to 14 carbon atoms and long chain fatty acid residues derived from fatty acids having from 16 to 22 carbon atoms.
U.S. Pat. No. 5,968,896 relates to a nutritional supplement containing a fat comprising at least two different fat sources of which one is an oil rich in monounsaturated fatty acids and the other is an oil rich in omega-3-fatty acids; and a therapeutic amount of antioxidant. The nutritional supplement is used for weight maintenance in individuals who are about to undergo major surgery in order to prevent or reduce postoperative complications.
Triglycerides are obtained from natural sources or they may be synthetically produced. Different processes have been developed in order to modify the fatty acid composition of triglycerides.
GB 791,165 relates to a method for the interesterification of fatty acid esters. The interesterification is performed by heating a mixture of substantially completely esterified fatty acid esters at a temperature of at least 180° C. in the presence of a plural metal soap catalyst, and thereby rearranging the fatty acid radicals in the mixture. The process according to this patent enables modification of triglycerides.
U.S. Pat. No. 6,124,486 relates to a process for making low calorie triglycerides. The process involves interesterifying short triglycerides having C2 to C10 fatty acid chains and long triglycerides having C16 to C24 fatty acid chains in the presence of a catalyst. The interesterification product mixture contains unreacted short and long triglycerides as well as individual triglycerides having at least one long and at least one short fatty acid chain. At least a substantial portion of the triglycerides has one long fatty acid chain and two short fatty acid chains. The low calorie triglycerides are then recovered from the reaction product mixture by removal of unreacted short and long triglycerides.
In the process according to U.S. Pat. No. 6,124,486 the trishort triglycerides are first removed from the reaction product mixture e.g. by evaporation. Then the remaining reaction product mixture is treated in a separation step to separate the low calorie triglycerides containing one or two long chains from unreacted trilong triglycerides and any remaining trishort triglycerides. The separation step is preferably performed in a short path still, a centrifugal molecular still or a high vacuum wiped film evaporator.
U.S. Pat. No. 6,369,252 relates to novel structured lipids and compositions comprising them as well as an enzymatic method for forming these structured lipids and mixtures. A synthetic triacylglycerol of the patent comprises at least one short chain fatty acid and at least one unsaturated fatty acid.
The prior art processes are not suitable for the preparation of pure mono- or dilong triglycerides. Only mixtures of mono- and dilong triglycerides are obtained. It is not easy to produce pure monolong triglycerides with a high yield in a one step separation process and it is impossible to produce pure dilong triglycerides in one step. It is not either possible with the prior art methods to produce pure triglycerides having a specific long fatty acid composition, which is optimal for any desired prospective use. The fractionation in the prior art is generally performed at temperatures below 270° C. Higher temperatures are generally avoided since when the separation processes are performed in the presence of an interesterification catalyst, the liquid being fractionated will at the same time undergo an interesterification reaction which continuously changes the product.
The triglyceride products obtained by the prior art chemical processes have a random fatty acid chain distribution and they include impurities such as trilong triglycerides which are not beneficial in some nutritional applications. Providing triglycerides with a certain kind of fatty acid chains as well as a specific distribution of long, medium and short chains is very difficult. Even enzymatic processes provide mixtures of triglyceride molecules.
It would be desirable to be able to produce triglycerides with various physical and chemical properties according to a predetermined pattern. However, the prior art is not exact enough for most purposes. Thus, there is a need for a method enabling the production of purer and more exactly designed triglycerides. There is especially a need for providing a process capable of producing triglycerides having a desired fatty acid chain length and composition so that any short, medium and/or long chain combination can be obtained on a commercial scale. The present invention aims at satisfying this need. There is a great interest in triglycerides in the industry and a desire to develop new triglycerides with special properties. However, the prior art processes do not enable the practitioner to obtain any target triglycerides at a level which is sufficient for practical use.